Attenuation-controlling device



June 1,1926. 1,587,363

0. B. BLACKWELL ATTENUATION CONTROLLING DEVICE Original Filed Oct. 25, 1919 AAAAAAAAAAAA "IvvvIvv IN VEN TOR.

k I ATTORNEY Patented .June 1, 1926."

UNITED STATES --1.587,363 PATENT v OFFICE.

crave a. BLAcxwnLL, or rnmnoma, New Yonx, .assrenon r AMERICA-IN manrnonn AND TELEGRAPH coMrANY, A coaronarron or new real.

A'IlTENUATION-CONTROLLING DEVICE.

Application filed October 21 5, 1919,8eria1 No. 883,281. Renewed March 1'l, 1988.

This invention relates to transmission systems and more particularly to transmission systems over which telephonic or multifrequency signals are transmitted. 5 It is often desirable in systems used for the transmission of frequencies varying over a considerable range to insert networks or combinations of impedances whichaffect the different frequencies in different amounts. Such an arrangement, for example, might be expedient where it is desired to cut out certain bands of frequencies so as to permit different frequency ranges to be used for different purposes. Further more, in transmission systems the attenuation usually varies for different frequencies,

and in the case of telephonic signals the higher frequencies are usually attenuated to such an extent as compared with the lower in a desired manner. It may be desirable .0 to include in transmission systems networks or impedance combinations for many other purposes in addition to those already specifically pointed out.

While it has been possible to devise many t-ions, such as wave filters or attenuation equalizers, which affect the different frequenciesin the desired manner, it has been difficult to satisfactorily associate these net-- works with the lines of a transmission system due to an interaction between the lines and networks resulting from the variations.

tion of interaction effects between such apparatus and the lines. In the arrangements of this invention the network or impedance device is included in a-circuit between two 5 one-way amplifiers, the input circuit of one frequencies'that a considerable degree of -cluding the two linesections L and L The line section L may represent a line types of networks or impedance .combina-,

transmission system without the introduc-' amplifier and the output circuit of the other amplifier being connected to different line sections of the transmission system. As the input circuits of the amplifiers are of a relatively high impedance, the association thereof with the line sections will cause no appreciable disturbance in the impedance relations existing between the line sections and their terminating equipment. .The network or impedance device may be thus associated withv the-system without the introduction of interaction effects or reflection losses and the amplifying arrangements will furthermore serve to make up any transmission losses due to the network or im-' pedance device itself. Furthermore as the association of the device or network with a line section may thus'be attained without effect on the line section, the line section may be terminated in any desired manner.

Other and further features of the invention may be clear from the following detailed description of the invention.

In the drawing is illustrated a circuit diagram embodying the arrangements of the invention, in the Figure 1 of which is illustrated one form of the invention and in the Fig. 2 is shown another form thereof.

In Fig. 1 is shown a transmission line insection over which electro-magnetic waves are being received and with which it may be desirable to connect a network of impedances to control the propagation characteristics of the circuit. Ifthis network or combination of impedances was associated directly with the line section and was of an impedance value other than that of the line section itself, there would be reflection lossesv introduced which .mightinterfere with the desired action in the circuit. Accordingly the line L is terminated in the im edance 1. If it is desired to obviate re action losses the impedance 1 mg be made approximately equal to the imp ance of lineL itself. In some instances it may not be desirable to entirely obviate reflection losses in the circuit and other reasons may make it desirable to terminate the line L, in an impedance of a value other than that of the line L itself. Accordingly the impedance value of element 1 is not fixed this invention as of a value equalto that the line L but my be of any desired whereby to huge in series with; line :D, is.- a'res stance 6 havcordinglycause no disturbance in the impedance relation existing between line L and its terminating impedance 1. Included between amplifier A and the input circuit of another repeater amplifier A is a network or combination of impedances, such as 3, the propagation characteristics of the circuit maybe controlled. Such a network might'be either a wave filter, or an attenuation equalizer, or any other combination of impedance desirable. The output circuit of amplifier A (or the output circuit of a series of amplifiers and networks if this is found desirable) may then be associated with the line section L Bridged across the output circuit of the last of the series'of amplifiers, such as A is the resistance 4 which is designed tohave a value small as compared to the impedance of the line section L In the arrangement as illustrated the network or attenuation controlling device, such as 3, will operate between the output impedance of. the amplifier A and the input impedance of the amplifier As these amplifiers are one-Way 'devices, the tenuation controlling device with the line sections in this manner will cause no inter action effects between the apparatus and the line sections. With this arrangement voltage variations may be taken from a line section, suchas L, with any desired terminal impedance efi'ect, desired frequency control, and may be thus applied to -another line section, such as L,.

.It is pointed out that in instances where interaction efiects' between the apparatus and the line L were not involved or where the impedance relation betweemthe apparatus 3 and line L was not of importance the amdplifier A and impedance omitte' and the line L connected directly to'apparatus 3. g

In ig. 2 is shown axmodification of the invention in whichtwo line sections L and L are interconnected by meansofan auxiliary-circuit including. the amplifiers A and A betweenthe: output and input circuits of whichlis included anattenuation' controlling device 8. Thejline...L,.. is slmwn as terminating-impart impedance eleme ti 5; similar dance 1 shown in Fig 1. Included the output circuit of the repeater association of the network or atmay be amplified with the 4 might be or current.

ing a value suflicientlysmall 56 that it does not affect the flow of currents over line L within the desired degree of approximation. Connected to theline L,' at the terminal points of resistance 6 is the input circuit of the vacuum bulb amplifier A Accordingly the voltage taken oif across resistance 6, which will be proportional to the current flowing overline L will be amplified by amplifier A changed'as desired by means of the attenuation device 8, and then impressed upon the input of amplifier A Included in the output circuit of amplifier A is the resistance 9-which has a value large in comparison with that of line L For purposes of might be of approximately 10,000 ohms and the line L might be of 500 ohms. Accord ingly any variation in the impedance characteristics of line L, would not have a very appreciable effect on the total impedance and would cause littledisturbance. on the electro-magnetic waves transmitted "from the amplifier A having the desired wave shape is established in line L pointed out that the values of the provide means for accomplishing this result with the following-features. The incoming line section may be terminated in any desirable manner. Voltages may then be taken off either across the line section or proportional to the current flowing in the ine .section without affecting appreciably the currents or voltages flowing 1n the line illustration resistance 9' In this manner a current,

section. These voltages may then be amplified and controlled by an impedance network in any desiredmanner in such a way as to. involve no reaction upon the line section impedance. The vol ages may then be impressed on the outg ing line section through such impedances as to prevent distortion of the voltage or current, orthrough any other impedances which might bring 'bout' any desired distortion of the voltage Accordingly, while theinvention has been disclosed as embodied in certainv specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many and widely varied forms without departing" from the spirit of the -invention as defined in the appendedclaims.

What is claimed is 1. An outgoing transmission line whose impedance may vary under different conditlons, a circuit associated therewith for impressing energy upon said line, means to interconnect said line and said circuit comprising a terminal impedance device, said device being so associated with said line and being so proportioned with respect to the line that the impedance of the combination consisting of the line and said impedance device as viewed from said circuit will not materially differ from the impedance of said device.

2. An outgoing transmission line whose impedance may vary under difi'erent conditions, a circuit associated therewith for impressing energy upon said line, means to interconnect said line and said circuit comprising a terminal impedance device, said device being so associated with the line and its impedance being sufliciently different from that of the line that the impedance of the combination consisting of said line and said device as viewed from said circuit will not greatly differ from that of said device.

3. A transmission system including an incoming line section and an outgoing line section, an impedance device for terminating one of said line sections, a circuit for interconnecting said line sections, said circuit being so connected with respect to said line terminating impedance and being so proortioned with respect to said terminating impedance that the impedance of the combination consisting of the terminating impedance and the input impedance of said circuit as viewed from the line will not be greatly difl'erent from said terminating impedance alone, a second impedance device for interconnecting said circuit and said outgoing line, said second impedance device being so associated with the outgoing line and its impedance being so proportioned with respect to that of the line that the impedance of the combination consisting of the outgoing line and said second impedance element as viewed from the interconnecting circuit will not differ greatly from the impedance of said second impedance device considered alone.

4. A transmission system including an incoming line section and an outgoing line section, an impedance device for terminating one of said line sections, a circuit for interconnecting said line sections, said circuit being so connected with respect to said line terminating impedance and being so proportioned with respect to said terminating impedance that the impedance of the combination consisting of the terminating impedance and the input impedance of said circuit as viewed from the line will not be greatly different from the terminating impedance alone, a. second impedance device for interconnecting said circuit and said out going line, said second impedance device being so associated with the outgoing line and its impedance being so pro ortioned with respect to that of the line t at the impedance of the combination consisting of the outgoing line and said second impedance element as viewed from the interconnecting circuit will not diifer greatly from the impedance of said second impedance device considered alone, said interconnecting circuitalso including a device for controlling the propagation characteristics of waves transmitted from the incoming line through said circuit to the outgoing line and a one-way device on each side of said last mentioned means.

In testimony whereof, I have signed my name to this specification this 21st day of October, 1919.

OTTO B. BLAOKVVELL. 

